This invention relates to sewing machines and more particularly to an improved low inertia presser system therefor and is especially useful for very high speed sewing machines.
In sewing machines having feed dog work feeding mechanism that is raised above the level of a work supporting throat plate, advanced and then dropped beneath the level of the throat plate, a presser mechanism acts to press the plies of the fabric work against the throat plate in cooperation with the feed dog. When the feed dog is above the top surface of the throat plate, it grips the work against the presser foot and lifts the presser foot and presser bar which must also drop with the feed dog until the downward movement of the work is arrested by the throat plate. Thus, the presser mechanism must respond rapidly to and follow the rising and falling movements of the feed dog in order to have effective and proper work feed. Moreover, the presser mechanism must also be capable of readily passing over hems and other obstructions in the material being sewn. As the speed of sewing is increased, it becomes progressively more difficult to return the presser foot quickly and forcably down upon the work at the end of the feed advance cycle of the feed dog. It is therefore desirable that the loads imposed on the feed dog be as light as possible so that the inertia forces acting on the presser mechanism be minimized so as to prevent an upward overthrow of the presser foot after the rise of the feed dog which would result in failure of the presser mechanism to oppose the feed dog consistently during the work advance stroke thereof. A number of low inertia presser devices are known in the art for minimizing these forces. Examples of such devices are illustrated in Ritter, U.S. Pat. No. 2,344,414; Becker, U.S. Pat No. 2,401,216; Ritter, U.S. Pat. No. 2,550,499; Johnson, U.S. Pat. No. 2,616,382; Rockerath, U.S. Pat. No. 2,827,006; Walling, U.S. Pat. No. 3,495,560 and Japanese Utility Model Reg. No. 845,812.